128 



OSTEOLOGY 



Cervical ribs derived from the seventh cervical vertebra (page 83) are of not infrequent occur- 

 rence, and are important clinically because they may give rise to obscure nervous or vascular 

 symptoms. The cervical rib may be a mere epiphysis articulating only with the transverse process 

 of the vertebra, but more commonly it consists of a defined head, neck, and tubercle, with or 

 without a body. It extends lateralward, or forward and lateralward, into the posterior triangle 

 of the neck, where it may terminate in a free end or may join the first thoracic rib, the first costal 

 cartilage, or the sternum. 1 It varies much in shape, size, direction, and mobility. If it re^ch 

 far enough forward, part of the brachial plexus and the subclavian artery and vein cross over 

 it, and are apt to suffer compression in so doing. Pressure on the artery may obstruct the circula- 

 tion so much that arterial thrombosis results, causing gangrene of the finger tips. Pressure on 

 the nerves is commoner, and affects the eighth cervical and first thoracic nerves, causing paralysis 

 of the muscles they supply, and neuralgic pains and paresthesia in the area of skin to which they 

 are distributed : no oculopupillary changes are to be found. 



The thorax is frequently found to be altered in shape in certain diseases. 



In rickets, the ends of the ribs, where they join the costal cartilages, become enlarged, giving 

 rise to the so-called "rickety rosary," which in mild cases is only found on the internal surface 

 of the thorax. Lateral to these enlargements the softened ribs sink in, so as to present a groove 

 passing downward and lateralward on either side of the sternum. This bone is forced forward 

 by the bending of the ribs, and the antero-posterior diameter of the chest is increased. The ribs 

 affected are the second to the eighth, the lower ones being prevented from falling in by the pres- 

 ence of the liver, stomach, and spleen; and when the abdomen is distended, as it often is in rickets, 

 the lower ribs may be pushed outward, causing a transverse groove (Harrison's sulcus) just 

 above the costal arch. This deformity or forward projection of the sternum, often asymmetrical, 

 is known as pigeon breast, and may be taken as evidence of active or old rickets except in cases 

 of primary spinal curvature. In many instances it is associated in children with obstruction in 

 the upper air passages, due to enlarged tonsils or adenoid growths. In some rickety children or 

 adults, and also in others who give no history or further evidence of having had rickets, an opposite 

 condition obtains. The lower part of the sternum and often the xiphoid process as well are deeply 

 depressed backward, producing an oval hollow in the lower sternal and upper epigastric regions. 

 This is known as funnel breast (German, Trichterbrust) ; it never appears to produce the least 

 disturbance of any of the vital functions. The phthisical chest is often long and narrow, and with 

 great obliquity of the ribs and projection of the scapulae. In pulmonary emphysema the chest is 

 enlarged in all its diameters, and presents on section an almost circular outline. It has received 

 the name of the barrel-shaped chest. In severe cases of lateral curvature of the vertebral column 

 the thorax becomes much distorted. In consequence of the rotation of the bodies of the vertebrae 

 which takes place in this disease, the ribs opposite the convexity of the dorsal curve become 

 extremely convex behind, being thrown out and bulging, and at the same time flattened in front, 

 so that the two ends of the same rib are almost parallel. Coincidently with this the ribs on the 

 opposite side, on the concavity of the curve, are sunk and depressed behind, and bulging and 

 convex in front. 



THE SKULL. 



The skull is supported on the summit of the vertebral column, and is of an 

 oval shape, wider behind than in front. It is composed of a series of flattened 

 or irregular bones which, with one -exception (the mandible), are immovably 

 jointed together. It is divisible into two parts: (1) the cranium, which lodges 

 and protects the brain, consists of eight bones, and (2) the skeleton of the face, 

 of fourteen, as follows: 



Occipital. 



Two Parietals. 



Frontal. 



Two Temporals. 



Sphenoidal. 



Ethmoidal. 



Cranium, 8 bones 



Face, 14 bones 



Skull, 22 bones f TWQ 



Two Maxillae. 



Two Lacrimals. 



Two Zygomatics. 



Two Palatines. 



Two Inferior Nasal Conchse. 



Vomer. 



Mandible. 



1 W. Thorburn, The Medical Chronicle, Manchester, 1907, 4th series, xiv, No. 3 



